Rice root exudates enhance desorption and bioavailability of phthalic acid esters (PAEs) in soil associating with cultivar variation in PAE accumulation.

Phthalic acid esters (PAEs) is a class of prevalent pollutants in agricultural soil, threating food safety through crop uptake and accumulation of PAEs. Accumulation of PAEs varies largely among crop species and cultivars. Nevertheless, how root exudates affect PAE bioavailability, dissipation, uptake and accumulation is still not well understood. In the present study, desorption and pot experiments were designed to investigate how root exudates from high-(Peizataifeng) and low-(Fengyousimiao) PAE accumulating rice cultivars affect soil PAE bioavailability, dissipation, and accumulation variation. Rice root exudates including low molecular weight organic acids (LMWOAs) of Peizataifeng and Fengyousimiao could enhance desorption of two typical PAE compounds, di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP), from aged soil to their available fractions by increasing soil dissolved organic carbon (DOC), thus improving their bioavailability in soil. Peizataifeng produced twice higher amounts of oxalic acid, critic acid and malonic acid in root exudates, and exhibited stronger effects on enhancing desorption and bioavailability of DBP and DEHP than Fengyousimiao. Higher (by about 50%) total organic carbon contents of root exudates from Peizataifeng led to higher (by 10-30%) soil microbial biomass carbon and nitrogen than Fengyousimiao, and thus promoted more PAE dissipation from soil than Fengyousimiao. Nevertheless, higher (by 20-50%) soil DOC and significantly higher PAE bioavailability in the soils planted Peizataifeng resulted in greater (by 53-93%) PAE accumulation in roots and shoots of Peizataifeng than Fengyousimiao, confirming by higher (by 1.82-3.48 folds) shoot and root bioconcentration factors of Peizataifeng than Fengyousimiao. This study reveals that the difference in root exudate extent and LMWOAs between Peizataifeng and Fengyousimiao differentiates PAE accumulation.

Effects of rice straw biochar on sorption and desorption of di-n-butyl phthalate in different soil particle-size fractions.

Sorption of organic contaminants by biochar greatly affects their bioavailability and fate in soils. Nevertheless, very little information is available regarding the effects of biochar on sorption and desorption of organic contaminants in different soil particle-size fractions. In this study, di-n-butyl phthalate (DBP), a prevalent organic contaminant in agricultural soils, was taken as a model contaminant. The effects of biochar on DBP sorption and desorption in six particle-size fractions (i.e., coarse sand, fine sand, coarse silt, fine silt, clay, and humic acid fractions) of paddy soil were investigated using batch sorption-desorption experiments. A straw-derived biochar with high specific surface area (116 m2/g) and high content of organic matter (OM) rich in aromatic carbon (67%) was prepared. Addition of this biochar (1% and 5%) significantly promoted the sorption and retention of DBP in all the paddy soil particle-size fractions at environmentally relevant DBP concentrations (2-12 mg/L) with 1.2-132-fold increase of the Kd values. With increasing addition rates of biochar, DBP retention by the biochar enhanced. The biochar's effectiveness was remarkably influenced by the physicochemical properties of the soil particle-size fractions, especially, the OM contents and pore size showed the most striking effects. A parameter (rkd) reflecting the biochar's effectiveness showed negative and positive correlations with OM contents and pore size of the soil particle-size fractions, respectively. Accordingly, strong effect of the biochar was found in the soil fractions with low OM contents and high pore size. The findings of this study gave insight into the effects and influencing factors of biochar on sorption and desorption of organic contaminants in soils at scale of various particle-size factions.

Variation in metabolism and degradation of di-n-butyl phthalate (DBP) by high- and low-DBP accumulating cultivars of rice (Oryza sativa L.) and crude enzyme extracts.

Crops can take up and accumulate di-n-butyl phthalate (DBP), an extensively used plasticizer with endocrine disrupting effect, which poses potential risk to human health. Our previous study found the genotype variation in accumulation of DBP by different cultivars of rice (Oryza sativa L.). Nevertheless, the effect of DBP metabolism in vivo on the accumulation variation among different plant cultivars remains unknown. In this study, metabolism variation of DBP by low (Fengyousimiao) and high (Peizataifeng) DBP-accumulating cultivars of rice and the key enzymes involving in DBP metabolism in rice plants were investigated using in vivo exposure of rice plants and in vitro exposure of root crude enzyme extracts. Both mono-n-butyl phthalate (MBP) and phthalic acid (PA) were detected as DBP metabolites in all rice tissues (i.e., roots, stems, leaves) and crude enzyme extracts with MBP predominance. DBP metabolism occurred simultaneously when DBP uptake with the highest metabolism in roots in vivo. Degradation of DBP in root crude enzyme extracts fitted well with the first order kinetics (R2 = 0.49-0.76, P < 0.05). The activity of carboxylesterase (CXE) in root crude enzyme extracts was significantly positively correlated with DBP degradation rates. CXE played an important role in DBP metabolism of rice plants, confirming by the fact that triphenyl phosphate of CXE inhibitor could inhibit DBP metabolism of in vivo and in vitro exposure. This result was further confirmed by in vitro degradation of DBP with the commercial pure CXE. The crude enzyme solution from roots of Fengyousimiao with higher CXE activity had significantly higher DBP degradation rates than that of Peizataifeng. However, Fengyousimiao with lower tolerance to DBP stress and higher inhibition by triphenyl phosphate displayed lower DBP metabolism ability in vivo than Peizataifeng.

Occurrence and distribution of antibiotics and antibiotic resistant genes in water and sediments of urban rivers with black-odor water in Guangzhou, South China.

Urban rivers in some countries have been heavily polluted and the water became black and odor. Nevertheless, only few studies reported the occurrence of antibiotics and their corresponding antibiotic resistant genes (ARGs) in urban rivers with black-odor water with and without remediation. In this study, nine antibiotics (belonging to sulfonamides, tetracyclines, quinolones, and macrolides) and their corresponding ARGs in water and sediments of six urban rivers in Guangzhou, South China were analyzed to investigate their spatial distribution and the influence of water remediation. The concentrations of individual antibiotics varied from ND (not detectable) to 2702 ng/L and ND to 449 µg/kg in surface water and sediments, respectively. Norfloxacin displayed the highest average concentrations, followed by ciprofloxacin. The relative abundance of quinolone-resistance gene qnrA (~103 ARGs/16S rRNA) was the highest, followed by tetracyclines-resistance genes tetC (~10-2 ARGs/16S rRNA). The antibiotics and ARGs in sediments from various rivers exhibited distinct spatial distribution with large variation from upstream to downstream. Generally, levels of antibiotics and tetracyclines-resistance genes (tetA, tetC and tetM) in urban rivers with black-odor water (affected by industrial and domestic sewage) were higher than those in remediated urban rivers. Significant positive correlations were observed only between the relative abundances of tetA (or tetC) with the concentrations of some antibiotics (e.g., ciprofloxacin and norfloxacin). TetA was also significantly positively correlated with the concentrations of Ni, Cr, and As in sediments. This study found that urban rivers remediated with dredging might lower antibiotic levels in sediment, but high relative abundance of certain ARGs (e.g., tetB, qnrA) may still exist.

Pt-Embedded CuO x-CeO2 Multicore-Shell Composites: Interfacial Redox Reaction-Directed Synthesis and Composition-Dependent Performance for CO Oxidation.

Exploring the state-of-the-art heterogeneous catalysts has been a general concern for sustainable and clean energy. Here, Pt-embedded CuO x-CeO2 multicore-shell (Pt/CuO x-CeO2 MS) composites are fabricated at room temperature via a one-pot and template-free procedure for catalyzing CO oxidation, a classical probe reaction, showing a volcano-shaped relationship between the composition and catalytic activity. We experimentally unravel that the Pt/CuO x-CeO2 MS composites are derived from an interfacial autoredox process, where Pt nanoparticles (NPs) are in situ encapsulated by self-assembled ceria nanospheres with CuO x clusters adhered through deposition/precipitation-calcination process. Only Cu-O and Pt-Pt coordination structures are determined for CuO x clusters and Pt NPs in Pt/CuO x-CeO2 MS, respectively. Importantly, the close vicinity between Pt and CeO2 benefits to more oxygen vacancies in CeO2 counterparts and results in thin oxide layers on Pt NPs. Meanwhile, the introduction of CuO x clusters is crucial for triggering synergistic catalysis, which leads to high resistance to aggregation of Pt NPs and improvement of catalytic performance. In CO oxidation reaction, both Ptδ+-CO and Cu+-CO can act as active sites during CO adsorption and activation. Nonetheless, redundant content of Pt or Cu will induce a strongly bound Pt-O-Ce or Cu-[O x]-Ce structures in air-calcinated Pt/CuO x-CeO2 MS composites, respectively, which are both deleterious to catalytic reactivity. As a result, the composition-dependent catalytic activity and superior durability of Pt/CuO x-CeO2 MS composites toward CO oxidation reaction are achieved. This work should be instructive for fabricating desirable multicomponent catalysts composed of noble metal and bimetallic oxide composites for diverse heterogeneous catalysis.

Contributions of distinct gold species to catalytic reactivity for carbon monoxide oxidation.

Small-size (<5 nm) gold nanostructures supported on reducible metal oxides have been widely investigated because of the unique catalytic properties they exhibit in diverse redox reactions. However, arguments about the nature of the gold active site have continued for two decades, due to the lack of comparable catalyst systems with specific gold species, as well as the scarcity of direct experimental evidence for the reaction mechanism under realistic working conditions. Here we report the determination of the contribution of single atoms, clusters and particles to the oxidation of carbon monoxide at room temperature, by the aid of in situ X-ray absorption fine structure analysis and in situ diffuse reflectance infrared Fourier transform spectroscopy. We find that the metallic gold component in clusters or particles plays a much more critical role as the active site than the cationic single-atom gold species for the room-temperature carbon monoxide oxidation reaction.

Uniform 2 nm gold nanoparticles supported on iron oxides as active catalysts for CO oxidation reaction: structure-activity relationship.

Uniform Au nanoparticles (∼2 nm) with narrow size-distribution (standard deviation: 0.5-0.6 nm) supported on both hydroxylated (Fe_OH) and dehydrated iron oxide (Fe_O) have been prepared by either deposition-precipitation (DP) or colloidal-deposition (CD) methods. Different structural and textural characterizations were applied to the dried, calcined and used gold-iron oxide samples. Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) showed high homogeneity in the supported Au nanoparticles. The ex situ and in situ X-ray absorption fine structure (XAFS) characterization monitored the electronic and short-range local structure of active gold species. The synchrotron-based in situ X-ray diffraction (XRD), together with the corresponding temperature-programmed reduction by hydrogen (H2-TPR), indicated a structural evolution of the iron-oxide supports, correlating to their reducibility. An inverse order of catalytic activity between DP (Au/Fe_OH < Au/Fe_O) and CD (Au/Fe_OH > Au/Fe_O) was observed. Effective gold-support interaction results in a high activity for gold nanoparticles, locally generated by the sintering of dispersed Au atoms on the oxide support in the DP synthesis, while a hydroxylated surface favors the reactivity of externally introduced Au nanoparticles on Fe_OH support for the CD approach. This work reveals why differences in the synthetic protocol translate to differences in the catalytic performance of Au/FeOx catalysts with very similar structural characteristics in CO oxidation.

Simultaneous determination by UPLC-MS/MS of seven bioactive compounds in rat plasma after oral administration of Ginkgo biloba tablets: application to a pharmacokinetic study.

A rapid, reliable, and sensitive method was developed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with an electrospray ionization (ESI) source for determination of seven bioactive compounds in rat plasma after oral administration of Ginkgo biloba tablets (GBTs). The method simultaneously detects bilobalide (BB), ginkgolide A (GA), ginkgolide B (GB), ginkgolide C (GC), quercetin (QCT), kaempferol (KMF), and isorhamnetin (ISR) for pharmacokinetic study. The analytes and internal standard (IS) were extracted from rat plasma by acetidin. An MS/MS detection was conducted using multiple reaction monitoring (MRM) and operating in the negative ionization mode. The calibration curve ranges were 5-500, 5-500, 2.5-250, 1-100, 1-100, 1-100, and 1-100 ng/ml for BB, GA, GB, GC, QCT, KMF, and ISR, respectively. The mean recovery of the analytes ranged from 68.11% to 84.42%. The intra- and inter-day precisions were in the range of 2.33%-9.86% and the accuracies were between 87.67% and 108.37%. The method was used successfully in a pharmacokinetic study of GBTs. The pharmacokinetic parameters of seven compounds were analyzed using a non-compartment model. Plasma concentrations of the seven compounds were determined up to 48 h after administration, and their pharmacokinetic parameters were in agreement with previous studies.

[Studies on evaluation of sustained release tablets of extracts of Ginkgo biloba releasing rate in vitro by pharmacological indicatrix].

Using sustained release tablets of Ginkgo bibolia extract as model drug,discuss technical feasibility of using biotic index to evaluate sustained release tablets. Chosing two pharmacological indicatrix: antioxidant ability and inhibition of platelet aggregation, to investigate the influence factors on experimental result, optimize the method and experiment condition, and set up pharmacological indicatrix evaluation method. Using those methods to determinate biological effects of dissolved liquid. Drawing release curves and biological effects curves, discussing their correlation. A good correlation was observed, illustrating that pharmacological indicatrix could evaluate sustained release tablets.